Thioxoethenylidene (CCS) as a bridging ligand

The reaction of [Mo(≡CBr)(CO)2(Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with [Fe2(μ-SLi)2(CO)6] affords, inter alia, the unsymmetrical binuclear thioxoethenylidene complex [Mo2(μ,σ(C):η2(C′S)-CCS)(CO)4(Tp*)2], which may be more directly obtained from [Mo(≡CBr)(CO)2(Tp*)] and Li2S. The reaction presumably proceeds via the intermediacy of the bis(alkylidynyl)thioether complex S{C≡Mo(CO)2(Tp*)}2, which was, however, not directly observed but explored computationally and found to lie 78.6 kJ mol–1 higher in energy than the final thioxoethenylidene product. Computational interrogation of the molecules [M2(μ-C2S)(CO)2(Tp*)2] (M = Mo, W, Re, Os) reveals three plausible coordination modes for a thioxoethenylidene bridge which involve a progressive strengthening of the C–C bond and weakening of the M–C and M–S bonds, as might be expected from simple effective atomic number considerations.This work was supported by the Australian Research Council (DP130102598 and DP110101611)

HD 219134 Revisited: Planet d Transit Upper Limit and Planet f Transit Nondetection with ASTERIA and TESS

HD 219134 is a K3V dwarf star with six reported radial-velocity discovered planets. The two innermost planets b and c show transits, raising the possibility of this system to be the nearest (6.53 pc), brightest (V = 5.57) example of a star with a compact multiple transiting planet system. Ground-based searches for transits of planets beyond b and c are not feasible because of the infrequent transits, long transit duration (~5 hr), shallow transit depths (<1%), and large transit time uncertainty (~half a day). We use the space-based telescopes the Arcsecond Space Telescope Enabling Research in Astrophysics (ASTERIA) and the Transiting Exoplanet Survey Satellite (TESS) to search for transits of planets f (P = 22.717 days and M sin i = 7.3 ± 0.04M_⊕) and d (P = 46.859 days and M sin i = 16.7 ± 0.64M_⊕). ASTERIA was a technology demonstration CubeSat with an opportunity for science in an extended program. ASTERIA observations of HD 219134 were designed to cover the 3σ transit windows for planets f and d via repeated visits over many months. While TESS has much higher sensitivity and more continuous time coverage than ASTERIA, only the HD 219134 f transit window fell within the TESS survey's observations. Our TESS photometric results definitively rule out planetary transits for HD 219134 f. We do not detect the Neptune-mass HD 219134 d transits and our ASTERIA data are sensitive to planets as small as 3.6 R_⊕. We provide TESS updated transit times and periods for HD 219134 b and c, which are designated TOI 1469.01 and 1469.02 respectively

Anhydrobiosis and Freezing-Tolerance:Adaptations That Facilitate the Establishment of Panagrolaimus Nematodes in Polar Habitats

<div><p>Anhydrobiotic animals can survive the loss of both free and bound water from their cells. While in this state they are also resistant to freezing. This physiology adapts anhydrobiotes to harsh environments and it aids their dispersal. <i>Panagrolaimus davidi</i>, a bacterial feeding anhydrobiotic nematode isolated from Ross Island Antarctica, can survive intracellular ice formation when fully hydrated. A capacity to survive freezing while fully hydrated has also been observed in some other Antarctic nematodes. We experimentally determined the anhydrobiotic and freezing-tolerance phenotypes of 24 <i>Panagrolaimus</i> strains from tropical, temperate, continental and polar habitats and we analysed their phylogenetic relationships. We found that several other <i>Panagrolaimus</i> isolates can also survive freezing when fully hydrated and that tissue extracts from these freezing-tolerant nematodes can inhibit the growth of ice crystals. We show that <i>P. davidi</i> belongs to a clade of anhydrobiotic and freezing-tolerant panagrolaimids containing strains from temperate and continental regions and that <i>P. superbus</i>, an early colonizer at Surtsey island, Iceland after its volcanic formation, is closely related to a species from Pennsylvania, USA. Ancestral state reconstructions show that anhydrobiosis evolved deep in the phylogeny of <i>Panagrolaimus</i>. The early-diverging <i>Panagrolaimus</i> lineages are strongly anhydrobiotic but weakly freezing-tolerant, suggesting that freezing tolerance is most likely a derived trait. The common ancestors of the <i>davidi</i> and the <i>superbus</i> clades were anhydrobiotic and also possessed robust freezing tolerance, along with a capacity to inhibit the growth and recrystallization of ice crystals. Unlike other endemic Antarctic nematodes, the life history traits of <i>P. davidi</i> do not show evidence of an evolved response to polar conditions. Thus we suggest that the colonization of Antarctica by <i>P. davidi</i> and of Surtsey by <i>P. superbus</i> may be examples of recent “ecological fitting” of freezing-tolerant anhydrobiotic propagules to the respective abiotic conditions in Ross Island and Surtsey.</p></div

Thioxoethenylidene (CCS) as a Bridging Ligand

The reaction of [Mo­(CBr)­(CO)₂(Tp*)] (Tp* = hydrotris­(3,5-dimethylpyrazol-1-yl)­borate) with [Fe₂(μ-SLi)₂(CO)₆] affords, inter alia, the unsymmetrical binuclear thioxoethenylidene complex [Mo₂(μ,σ­(<i>C</i>):η²(<i>C</i>′<i>S</i>)-CCS)­(CO)₄(Tp*)₂], which may be more directly obtained from [Mo­(CBr)­(CO)₂(Tp*)] and Li₂S. The reaction presumably proceeds via the intermediacy of the bis­(alkylidynyl)­thioether complex S­{CMo­(CO)₂(Tp*)}₂, which was, however, not directly observed but explored computationally and found to lie 78.6 kJ mol^–1 higher in energy than the final thioxoethenylidene product. Computational interrogation of the molecules [M₂(μ-C₂S)­(CO)₂(Tp*)₂] (M = Mo, W, Re, Os) reveals three plausible coordination modes for a thioxoethenylidene bridge which involve a progressive strengthening of the C–C bond and weakening of the M–C and M–S bonds, as might be expected from simple effective atomic number considerations

Thioxoethenylidene (CCS) as a Bridging Ligand

The reaction of [Mo­(CBr)­(CO)₂(Tp*)] (Tp* = hydrotris­(3,5-dimethylpyrazol-1-yl)­borate) with [Fe₂(μ-SLi)₂(CO)₆] affords, inter alia, the unsymmetrical binuclear thioxoethenylidene complex [Mo₂(μ,σ­(<i>C</i>):η²(<i>C</i>′<i>S</i>)-CCS)­(CO)₄(Tp*)₂], which may be more directly obtained from [Mo­(CBr)­(CO)₂(Tp*)] and Li₂S. The reaction presumably proceeds via the intermediacy of the bis­(alkylidynyl)­thioether complex S­{CMo­(CO)₂(Tp*)}₂, which was, however, not directly observed but explored computationally and found to lie 78.6 kJ mol^–1 higher in energy than the final thioxoethenylidene product. Computational interrogation of the molecules [M₂(μ-C₂S)­(CO)₂(Tp*)₂] (M = Mo, W, Re, Os) reveals three plausible coordination modes for a thioxoethenylidene bridge which involve a progressive strengthening of the C–C bond and weakening of the M–C and M–S bonds, as might be expected from simple effective atomic number considerations

Thioxoethenylidene (CCS) as a Bridging Ligand

The reaction of [Mo­(CBr)­(CO)₂(Tp*)] (Tp* = hydrotris­(3,5-dimethylpyrazol-1-yl)­borate) with [Fe₂(μ-SLi)₂(CO)₆] affords, inter alia, the unsymmetrical binuclear thioxoethenylidene complex [Mo₂(μ,σ­(<i>C</i>):η²(<i>C</i>′<i>S</i>)-CCS)­(CO)₄(Tp*)₂], which may be more directly obtained from [Mo­(CBr)­(CO)₂(Tp*)] and Li₂S. The reaction presumably proceeds via the intermediacy of the bis­(alkylidynyl)­thioether complex S­{CMo­(CO)₂(Tp*)}₂, which was, however, not directly observed but explored computationally and found to lie 78.6 kJ mol^–1 higher in energy than the final thioxoethenylidene product. Computational interrogation of the molecules [M₂(μ-C₂S)­(CO)₂(Tp*)₂] (M = Mo, W, Re, Os) reveals three plausible coordination modes for a thioxoethenylidene bridge which involve a progressive strengthening of the C–C bond and weakening of the M–C and M–S bonds, as might be expected from simple effective atomic number considerations